1. Field of the Invention
The present invention relates to an ionic compound, and a pressure-sensitive adhesive and a polarizer both comprising the ionic compound, and particularly to an ionic compound having anti-static effect, and an anti-static pressure-sensitive adhesive and polarizer in which the ionic compound is utilized.
2. Description of the Prior Art
A liquid crystal display (LCD) device generally includes a liquid crystal panel and a polarizer adhered to the Liquid crystal panel through an adhesive layer. The pressure-sensitive adhesive layer is disposed on the outmost surface of the polarizer. A release film is further disposed on the pressure-sensitive adhesive layer for protecting it and the polarizer. Before the adhesion of the polarizer to the liquid crystal panel is carried out, the release film is peeled so as to be removed from the polarizer to expose the pressure-sensitive adhesive layer for the adhesion.
Because the pressure-sensitive adhesive layer and the release film are both made of plastic, static charges may accumulate on the pressure-sensitive adhesive layer upon removal of the release film. When the liquid crystal is subjected to a working voltage under the situation that static charges remain on the pressure-sensitive adhesive layer, the liquid crystal molecules tend to lose alignment ability. This leads to a low yield of the LCD device. Accordingly, it needs an anti-static process for the pressure-sensitive adhesive layer to avoid the aforesaid problem.
For conventional technology, the anti-static process for the pressure-sensitive adhesive layer may include adding an anti-static agent therein or disposing an anti-static layer on the exterior of the polarizer. However, compared with coating an anti-static layer on the exterior of the polarizer, directly adding an anti-static agent in the pressure-sensitive adhesive layer may obtain a better effect.
Currently known anti-static agents include metal powder, fine carbon particulates, ionic liquid or surfactant. For effectively preventing the pressure-sensitive adhesive layer from occurrence of static charges, a great amount of metal powder or fine carbon particulates should be added in the pressure-sensitive adhesive layer. However, the great amount of metal powder or fine carbon particulates will cause the decrease of the transparency of the pressure-sensitive adhesive layer. And that will reduce the brightness of the LCD device. Surfactant tends to migrate to the surface of the pressure-sensitive adhesive layer. And that will deteriorate the adhesion performance of the pressure-sensitive adhesive layer. Also, the surfactant tends to be affected by humidity and then become uncontrollable. Ionic liquid, such as alkali metal salt, or fluoro-organic anion salt, is incompatible with the polymer of the pressure-sensitive adhesive, which will lead to unsuitable anti-static effect for the pressure-sensitive adhesive or defects of physical properties or appearance of the pressure-sensitive adhesive layer.